1. Field of the Invention
This invention relates generally to dental processes and systems and, more specifically, to an In-situ Tooth Filling System and Method Utilizing External Curing Step.
2. Description of Related Art
Conventional tooth repair approaches can typically be grouped into two categories: (1) those conducted in the dentist's office in a single visit (e.g. fillings), and (2) those requiring an intermediate step conducted at a dental lab (e.g. dental prosthetics). As depicted in FIG. 1, the typical in-situ filling method 10 proceeds through the following steps: the tooth having the cavity is first drilled out to create a clean void that is suitable for filling 100. The dentist then injects a filling material (composite, metal or other) into the void previously created in the tooth 102. For fillings made from composite, the material must be cured once it has been injected so that it is hard enough to function as a repair for the tooth. The injection and curing of the composite material is typically done in layered steps 104. Generally a light-reactive filling material is used, with ultraviolet wavelength being the most common. Once filled and cured, the dentist shapes and polishes the filling 106 so that the patient has a comfortable bite and no sharp or rough edges. Rosenfeld, U.S. Pat. No. 7,189,076 discusses a typical layered filling and curing method for in-situ tooth filling.
The in-situ filling method is by far the most prevalent approach used to repair a person's tooth because it is completed in a single office visit, and because it therefore tends to be the lowest-cost method available. In-situ tooth fillings are commonly covered by dental insurance. The problems with the in-situ filling method are related to durability and comfort. Because the composite material used to fill the tooth is cured while in the tooth, the dentist cannot use the type of composite material that is heat-cured in an oven, or make sure that the composite material used is totally cured and hardened. The heat-curable/light-curable composite material is used to create one of the hardest and most durable finished dental prosthetics available. Furthermore, during in-situ filling there will be air bubbles and gaps between the filling and the walls of the void created in the tooth during the filling process. These gaps are the result of the slight shrinkage that occurs during the curing process. Any gaps between the filling and the tooth will result in tooth discomfort for the patient and a potential for bacterial impregnation (which further reduces the fillings lifespan).
In cases where filling the tooth in the dentist's office is either not desirable, or it is not feasible, a prosthetic filling (or tooth) is installed. FIG. 2 depicts the steps employed in a conventional dental prosthetic installation method 12.
First, an impression of the undisturbed tooth is made 108. Next, 100, the tooth is prepared for filling by drilling a clean void in the tooth. A second impression is then made 110; this impression is of the tooth after the void has been drilled. For now, these are the final steps conducted in the dentist's office during this visit (although a temporary filling will usually be installed to prevent undue discomfort for the patient and to keep the void clean.
At the dental prosthetics lab, the first and second impressions are used to make a single prosthetic shaped to fit perfectly into the void created in the patient's tooth 112. This prosthetic piece is then cured by heat (and sometimes partially by light) while being held in a vacuum state at the dental lab 114.
At a second appointment at the dentist's office, the prosthetic is installed into the void previously formed in the patient's tooth, and is held in place by specialized adhesive cement 116. Any shrinkage of the prosthetic that occurred during curing is compensated for by the dental adhesive used to permanently bond the prosthetic to the patient's tooth. The result is a perfectly-fitted repair area that is much less likely to cause the patient future discomfort or to suffer from a short lifespan. Examples of these conventional approaches are discussed in Hewell, U.S. Pat. No. 4,695,254, Rubbert (I), U.S. Pat. No. 7,708,557 and Rubbert (II), U.S. Patent Application Publication No. US12/0064489.
While prosthetic filling methods produce a very high quality result for the patient, they tend to be quite expensive and time-consuming. As a result, they are only chosen infrequently for tooth repair. What is needed is a tooth repair method and system that provides the comfort and durability of a dental prosthetic with the cost and convenience of an in-situ installed filling.